1. Field of the Invention
The present invention relates to a method and an apparatus for classifying repetitive defects on a substrate. More particularly, the present invention relates to an apparatus and method for classifying defects on dies of a substrate into repetitive defects and non-repetitive defects, and an apparatus for performing the method.
2. Description of the Related Art
Generally, a semiconductor device is manufactured under surroundings that include various contamination sources such as particles in air, contaminants generated from process equipment, reactants and/or products, etc. Thus, it is very difficult to find the contamination sources which provide defects in the semiconductor device, since hundreds of processes are performed in manufacturing a semiconductor device.
Meanwhile, the processes for manufacturing a semiconductor device include a photolithography process. According to the photolithography process, a pattern of a reticle is transcribed into a photoresist film over a semiconductor substrate using photolithography exposing equipment. The photolithography process includes an exposing process in which a light having a specific wavelength is irradiated onto the photoresist film through the reticle to expose the photoresist film, and a developing process in which a developing solution is provided to the exposed photoresist film to selectively remove the photoresist film. In this way, a photoresist pattern is formed on the semiconductor substrate. A layer on the semiconductor substrate is partially etched using the photoresist pattern as an etching mask to form a desired layer pattern on the semiconductor substrate.
Here, when the photolithography process is repeatedly performed using only one reticle, as shown in FIG. 1, particles generated from the photoresist film, etc., are continuously accumulated on the reticle. A light is reflected from the particles so that a path of the light is changed. Thus, as shown in FIG. 2, when the photoresist film is exposed using the reticle with accumulated particles thereon, defects such as a bridge are generated in the photoresist pattern.
Particularly, as shown in FIG. 3, when the exposing process is repeatedly carried out on dies positioned in a single shot region using the single reticle, the defects are repeatedly generated on substantially the same positions of the dies. For example, when the particles are attached to a ninth exposing portion of the reticle, the defects are repeatedly generated on each of the dies in the single shot region that is exposed by the ninth exposing portion of the reticle.
The repetitive defects are classified separately from all of the other defects on the semiconductor substrate so that the contamination of the reticle currently used is recognized. After the contamination of the reticle is recognized, the reticle is then cleaned or exchanged for new reticle. Therefore, to form a desired pattern on the semiconductor substrate, it is very important to classify the repetitive defects separately from all of the other defects on the photoresist pattern of each of the dies after performing the exposing process.
In a conventional method of classifying repetitive defects, a first die is sequentially compared with remaining dies. A second die is sequentially compared with the remaining the dies except the first die. A third die is sequentially compared with the remaining the dies except the first and second dies. This comparison is sequentially carried out on the all of the dies to classify repetitive defects separately from all of the other defects.
However, according to the conventional method, since any one die is compared with the remaining dies except previously compared dies, time for performing the conventional method is about 3 minutes to about 5 minutes. Thus, the time required for performing the conventional method is too long.
Also, for example, there is such a case that defects are repeatedly recognized on substantially same positions of each of first, second and third dies in a single shot region. However, the first, second and third dies are exposed by exposing portions of a reticle different from each other. Thus, the recognized defects do not correspond to repetitive defects.
However, in the conventional method, since the defects are not classified according to shot region, the recognized defects are mistakenly classified as the repetitive defects, and the normal reticle is determined to be abnormal. Due to this error, the normal reticle is cleaned or replaced with new reticle.